Those skilled in the art are generally cognizant of the use of wall-mounted file trays for aiding in the organization of documents and the like. For example, Bartholomew, U.S. Pat. No. 4,062,452, discloses thin, box-like receptacles that may be arranged on a wall in a vertically stacked row. A first or "primary" file tray is fastened to the wall. It is contemplated in Bartholomew that additional or "secondary" file trays can be added below the first file tray, with each file tray in the row being supported by the preceding one above it through mechanically interlocking parts. Although not discussed in Bartholomew, the structure shown therein would seem also to allow secondary file trays to be added above the primary file tray to be supported thereby.
Similarly, Bobrick, U.S. Pat. No. 4,162,014, discloses a primary file tray fastened to the wall with secondary file trays depending therefrom. Again, all of the secondary file trays are ultimately dependent on the primary file tray for their support. With the file tray of Bobrick, secondary file trays can be added above the primary file tray only by first removing the primary file tray and, in effect, reinstalling it as a secondary file tray depending from a higher, newly installed primary file tray.
Other U.S. patents that disclose the general concept of wall-mounted file trays include Karkut, U.S. Pat. No. 3,430,774; Rorex, U.S. Pat. No. 4,081,080; Genn, et al., U.S. Pat. No. 4,083,456; and Olivan, U.S. Pat. No. 4,099,813. Neither these patents nor Bobrick disclose a wall-mounted file tray of simple design adapted to be added to either the top or bottom of a vertical array of such wall-mounted file trays without the need to remove any of the file trays already mounted in order to install an additional one.